METHODS OF DETERMINING CATION EXCHANGE SITES OCCUPED BY CRUDE OIL AND THE WETTABILITY OF CATION EXCHANGE SITES IN ROCK CORE SAMPLES IN A NON-PRESERVED STATE

摘要

A method for determining properties of different cation exchange sites in a rock core sample, at a non-preserved state of the rock core sample may include providing a rock core sample in a non-preserved state; displacing all native components out of the rock core sample; subjecting the rock core sample clean of native components to a plurality of coreflooding steps to determine a total amount of exchangeable cations adsorbed onto the cation exchange sites when the rock core sample is clean of native components; injecting formation brine and then a reservoir crude oil into the rock core sample until reaching irreducible water saturation and equilibrium between formation brine, the reservoir crude oil, and the cation exchange sites, such that rock core sample includes a plurality of indigenous exchangeable cations adsorbed onto the cation exchange sites, a plurality of cation exchange sites occupied by a crude oil, and one or more fluids occupying pore spaces in the rock core sample; subjecting the rock core sample to a plurality of coreflooding steps, the plurality of coreflooding step displacing the plurality of indigenous exchangeable cations, the crude oil, and the one or more fluids in at least two separate coreflooding steps to render the rock core sample clean of the indigenous cations; determining an amount of indigenous exchangeable cations adsorbed onto the cation exchange sites; and determining at least one property of different cation exchange sites in the rock core sample based on the amount of indigenous exchangeable cations and the total amount of exchangeable cations.